Treatment of viscose solutions



' r I and the subsequent ageing Patenteddan. 19;, .1932 i rnnnnmox'w srnnn, Jnqjorrri 'rsiiunen, I V g p Koreans com any, A coaroi nrron or earn-when tamsnvlma,

' marine:Mn v'r or viscose soLurrIoNs' 1 No Drawing.

This invention relates to the preparation of viscose solutions" and, more" particularly, to the preparation of viscose-solutions by the common Xanthate process. 5 j s .An object of my invention is toprovide a processof, converting certain objectionable compounds formed in the preparationof cel-' lulose solutions, into unobjectionable, sub g V v I I a cose of proper vlscosityfor sp nning filaments stances. r

A second object of my invention is to pres ventth'e liberation of noxious gases during precipitation cellulose from viscose solutlons. a g c A further object of my invention isto provide a process of producing alighter colored viscose than is produced by prior processes. In the preparation of viscose according to that process in which cellulose is dissolved and converted to sodium cellulosez'zzanthate,

certain by-produ'cts are produced which will decompose when the solution isbrought into the presence of an able and noxious gases, hydrogen sulphide. v

I have discoveredthat thesexobjectionable compounds may be converted. into a form not subject to decomposition \vith evolution of hydrogen sulphide iupon acidification, A by means of a novel agent and procedure Inorder that myinvention may be clearly set forth and understood, I will now describe the preferredmanner in which my invention is practiced, including, by wayof illustra tion, the usual method of preparation of viscose solutions.- c I w Cotton linters, chemical wood pulp, or other suitable form of cellulose, is treated with a strong solution of sodium hydroxide, I I I I other substances falling with nthevscopeof is,d s e .,i uh a a at ol, f 0mino 'para -aminophenol, and the like, "suohior usually of 15 to 20% conc'entration'ata temperaturebetween 15 and'QO". 6.: The-excess caustic solution is pressed out and thee-treated cotton is allowed to age at lowtenip'era-tures for several days. It is then treated in suitable mixing apparatus With: carbon b-isulphide, with the resultant formation. of sodium cellulose Xanthate. Duringthis stage of the sodium cellulose Xanthate, sodium sulphide and. sodium thiocarbonate are acid, liberating-objection such; for nstance, as

; inarily vto be formed in the viscose 'Solution as by-products. If such a solution, after ageing but ivit lioutlfurther treatmenh-islspun t i lnto orothervvise treated wvith,.anacid pre'cipil tation bath, hydrogen sulphide? isevol'ved by reactionoit' theacid-With saidsodiumsulphide and sodium thiocarbonate; This gas, when liberated 1n the'spinmng rooms, is mostob;

jection'ablea. v

, have found that, vvhenlafsolution ofvisto induce considerable-aeration, orcotherwise aerated, preferably: for'5r-to :7 hours, and at. 05.

a temparture preferably over 20{ G.,[said' c sulphur compounds beco'nvertedixito a form not subject to. decompositionlyvith liberation ofhydrogensulphide upon acidifica: I tion of the viscose solution-j, uponibeing-spun 7.0 into an acid precipitation ormiking bath, or thelike'ic' f V i he compounds which I, have found suitable for-my purpose are, ofboth organic and inorganic nature. {In my copending-applica; tion', Serial No.;124,5 56,fi ledjJuly 24:, 1926, ll have shown that @When a solution. containing" soluble alkali metal sulphide is aerated in the l V v presence of limited amounts of certain metallic salts, such, for example, as iron oxide,.cobalt sulphide or nickel sulphide, said soluble alkali metal sulphide can be converted into a more stable form, 'i."e.-,alkali' metal thiosul phate. ,Irhave also found that aromatic ring compounds containing a plurality of 'substituted groups, at least one of which is a .hydroxyl (QH) group, maybe used WhileI preferito use hydroquinone ,;l "may also use genie mpq n sar u bi c -ioneblfa nd preferred f as compared Wltll metallic salts. When using, such organic data- Y lysts, I prefertof use formAOt BOmgQ. tea

catalystper literof viscosesolution,although f greater or lesser quantitiesmay bet-required} j for specialgconditionsa i g The r sultswhich,obtainlaccordingtom f As er wosm invention are iillustratedflby the following eX-iwe g ample: A solution of viscose containing, when of hydrogen sulphide is given as by weight of the original viscose solution).

A probable explanation of the above phenomena is that the objectionable sulphur comv pounds r'ormed in the viscose solution due to side reactions of sodium hydroxide and carbon hisulphide or to decomposition/of the xanthate duringlageing or during the aera tion in the presence of my catalyst are oxidized to compounds such as sodium thiosulphate which are not hydrolyzed or decomposed by acids withliberation of hydrogen sulphide. i

According to my invention, liberation of noxious gases during spinning or precipitation'of the viscose may be substantially elim-' inated.. r

.A'further advantage gained bvtheuse of these catalysts is that the dark orange, or

brown, color of the normal viscose solution is changed to an appreciably lighter color, resulting in the i ormation of a whiter filament orthread.

;.My invention is not limited .to the specific examples given hereinabove byway of illustration but may be variously embodied and practiced within the scope of the following claims;

1 cl as my invention:

. 1. The processlof preventing the liberation of hydrogen sulphide in the precipitation of a viscose solution by an acid. which comprises aerating said solution, prior to, precipitation thereof. in the presence of a catalvstrwhich promotes the conversion of the objectionable sulphur compounds into other compounds which do. not liberate hydrogensulphide in the presence of an acid. Y

'2. The process of preventing the liberationof hydrobensulphide in the precipitation of a. viscose solution b an acid whiclrcomprises aerating said solution, prior to. precipitation thereof. in the presence of an arc matic ringrcompound. containing a plurality of substitutedgroups, atleastjone ofwhich is hydroxyl group.

r 3. The process of treating a viscose solution prior toprecipitation thereof which comprisesaer ating it, in the'presence of hydroquinone. I 1

4. The process of treating. a viscosesolu tion whichrcomprises a-erating'it at a temperature above 20 C. in, the presence of hydroquinone. Y

, 5. The process of treatinga viscose solu- 7 tion prior. to the precipitation thereoi't which comprises aerating it for over five hours in the presence of hydroquinone.

6. The process of treating a viscose solution prior to precipitation thereof, which comprises aerating it at a temperature of over 20 C. in the presence of from 40 to mg. of hydroquinone per liter of solution.

7 The process of treating a viscose solution containing sodium sulphide and sodium thiocarbonate which comprises aerating the solution in the presence of a catalyst effective to promote the conversion of said sodium S1111 phide and sodium thiocarbonate into compounds which will not liberate hydrogen sule phide in the presence of acid. p

8. Theproces's of treating a solution comprising in part sodium sulphide and sodium thiocarbonateiwhich comprises aerating the solution in the presence of a catalyst effective to promote the conversion of said sodium sulphide and sodium thiocarbonate intocompounds which will not liberate hydrogen sulphide in the presence of acid.

7 9. The process of treating a solution comprising in part sodium thiocarbonate which comprises aerating the solution in the presence of a catalyst effective to promote the conversion of said sodium thiocarbonate into compounds which will not liberate hydrogen sulphide in the presence of acid. v

10. The process of treating a viscose solutioncontaining sodium sulphide and sodium thiocarbonate' which comprises aerating the solution in the presence of an organic catation containing sulphur in a form subject to decomposition upon acidification of said solution, resulting in the liberation of hydrogensulphide, which comprises aerating said solution in the presence of a catalyst to bring said sulphur into'a form which will not liberate hydrogen sulphide upon acidification'of said solution, 7

In testimony whereof, I have hereunto subscribed my name this 7th day of anuary,

FREDERICK W. SPERR, JR. 

